The invention relates generally to combustors, and more particularly to a premixing device for application in low emission combustion processes.
Various types of combustors are known and are in use. For example, can type, can-annular or annular combustors are employed in aeroderivative gas turbines for applications such as power generation, marine propulsion, gas compression, cogeneration, offshore platform power and so forth. Typically, the combustors for the gas turbines are designed to minimize emissions such as NOx and carbon dioxide emissions.
In certain traditional systems, the reduction in emissions from the combustors is achieved through premixed flames. The fuel and air are mixed prior to combustion and the mixing is achieved by employing cross-flow injection of fuel and subsequent dissipation and diffusion of the fuel in the air flow. Typically, fuel jets are positioned between vanes of a swirler or on the surface of the vane airfoils. However, this cross-flow injection of fuel generates islands of high and low concentrations of fuel-to-air ratios within the combustor, thereby resulting in substantially high emissions. Further, such cross-flow injection results in fluctuations and modulations in the combustion processes due to the fluctuations in the fuel pressure and the pressure oscillations in the combustor that may result in destructive dynamics within the combustion process.
Similarly, in certain other systems that require premixing of air and a gaseous fuel prior to combustion, it may be challenging to reduce the emissions and the pressure fluctuations within a combustion area. For example, in gas range systems diffusion flames result in high levels of emissions and relatively inefficient operation as the degree of premixing required for such processes is difficult to achieve.
Accordingly, there is a need for a premixer for lean operation of combustors employed in gas turbines while achieving reduced NOx emissions from the combustor. It would also be advantageous to provide a combustor for a gas turbine that will work on a variety of fuels, while maintaining acceptable levels of pressure fluctuations within the combustor. Furthermore, it would be desirable to provide a combustor having capability of employing high or pure hydrogen as fuel without the occurrence of flashbacks or burnouts.